In conventional GPS receivers, a spread spectrum correlator correlates the received GPS signal with a reference signal. In multi-path environments, however, a line of sight (LOS) GPS signal is combined with delayed multi-path GPS signals which make it difficult to track the LOS signal. Conventional spread spectrum correlators are able to track the LOS GPS signal when the delays of the multi-path signals are greater than one code chip of the GPS coarse/acquisition (CA) code.
In certain multi-path environments (e.g. urban canyon environments), however, multi-path GPS signals may have delays of less than one code chip. In these multi-path environments, the conventional correlation peaks of the LOS and multi-path GPS signals smear together and are not distinguishable. Thus, the conventional correlator has difficulty resolving and tracking the LOS GPS signal.